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United States Patent |
6,237,235
|
Feist
,   et al.
|
May 29, 2001
|
Electronic level and process for video sighting
Abstract
An electronic level comprising a clinometer, an image receiving device
having a telescope with an objective and with a CCD receiver matrix and
with a screen for displaying the image of a graduated staff which is set
up at a target and provided with a coded graduation. A vertical axis is
rotatable about the level. A leveling device is included for alignment and
rough leveling of the level with respect to the graduated staff. An input
unit is provided for entering measurement data. A power supply unit and a
computer is included for processing the measurement data, calculating
measurement values and for image evaluation. The image receiving device
comprises a CCD receiver matrix which is preferably operated in video
clock. The objective or the CCD receiver matrix is arranged in a fixed
position relative to the vertical axis, and objective and CCD receiver
matrix are adjustable relative to one another, and the clinometer is
assigned in a fixed manner for measuring the deviation of the position of
a sighting axis relative to the horizon, wherein the sighting axis is
formed by a center pixel of the CCD receiver matrix.
Inventors:
|
Feist; Wieland (Jena, DE);
Monz; Ludwin-Heinz (Jena, DE);
Kaschke; Michael (Oberkochen, DE)
|
Assignee:
|
Carl Zeiss Jena GmbH (Jena, DE)
|
Appl. No.:
|
350857 |
Filed:
|
July 9, 1999 |
Foreign Application Priority Data
| Jul 29, 1998[DE] | 198 33 996 |
Current U.S. Class: |
33/295; 33/290 |
Intern'l Class: |
G01C 015/02 |
Field of Search: |
33/290,291,292,293,294,295
|
References Cited
U.S. Patent Documents
4343550 | Aug., 1982 | Buckley et al. | 33/293.
|
4488050 | Dec., 1984 | Iwafune | 33/293.
|
5272814 | Dec., 1993 | Key | 33/290.
|
5402223 | Mar., 1995 | Schlobohm et al. | 33/294.
|
5551159 | Sep., 1996 | Mooty | 33/294.
|
5777899 | Jul., 1998 | Kumagai | 33/291.
|
6023326 | Feb., 2000 | Katayama et al. | 33/290.
|
6055046 | Apr., 2000 | Cain | 33/291.
|
6108919 | Aug., 2000 | Wu et al. | 33/292.
|
Primary Examiner: Bennett; G. Bradley
Attorney, Agent or Firm: Reed Smith LLP
Claims
What is claimed is:
1. An electronic level comprising:
a clinometer;
an image receiving device having a telescope with an objective and with a
CCD receiver matrix and with a screen for displaying the image of a
graduated staff which is set up at a target and provided with a coded
graduation;
a vertical axis about which the level rotates;
a leveling device for alignment and rough leveling of the level with
respect to the graduated staff;
an input unit for entering measurement data;
a power supply unit and a computer for processing the measurement data,
calculating measurement values and for image evaluation;
said image receiving device comprising said CCD receiver matrix which is
operated in video time;
said objective or said CCD receiver matrix being arranged in a fixed
position relative to the vertical axis;
said objective and CCD receiver matrix being adjustable relative to one
another; and
the clinometer being assigned in a fixed manner for measuring the deviation
of the position of a sighting axis relative to the horizon;
wherein the sighting axis is formed by a center pixel of the CCD receiver
matrix.
2. The level according to claim 1, wherein the measurement axes of the
clinometer are perpendicular to one another and one measurement axis is
vertical to the sighting axis or at a fixed angle thereto, wherein the
clinometer is connected with the computer.
3. The level according to claim 1, wherein the front principal point of the
objective lies in the intersection of the sighting axis and vertical axis
or at a fixed distance s from this intersection.
4. The level according to claim 1, wherein the CCD receiver matrix and the
objective are displaceable relative to one another by adjusting means or a
drive in the direction of the optical axis of the objective for focusing
the graduated staff image, wherein the CCD receiver matrix or the
objective are in a fixed position, and wherein the displacement path and
the displacement direction of the matrix and/or of the objective can be
determined from the image data supplied by the receiver elements of the
matrix by an imaging evaluating system.
5. The level according to claim 1, wherein the display unit is provided
with a screen which has a diaphragm for blocking out ambient light,
wherein an arrangement is provided which controls the contrast of the
screen depending on the ambient light and is connected with the computer.
6. A process for video sighting with a level having:
a clinometer;
an image receiving device having a telescope with an objective and with a
CCD receiver matrix and with a screen for displaying the image of a
graduated staff which is set up at a target and provided with a coded
graduation;
a vertical axis about which the level rotates;
a leveling device for alignment and rough leveling of the level with
respect to the graduated staff;
an input unit for entering measurement data;
a power supply unit and a computer for processing the measurement data,
calculating measurement values and for image evaluation;
said image receiving device comprising said CCD receiver matrix which is
operated in video time;
said objective or said CCD receiver matrix being arranged in a fixed
position relative to the vertical axis;
said objective and CCD receiver matrix being adjustable relative to one
another; and
the clinometer being assigned in a fixed manner for measuring the deviation
of the position of a sighting axis relative to the horizon;
wherein the sighting axis is formed by a center pixel of the CCD receiver
matrix and wherein a graduated staff arranged at a distant target is
sighted, said process comprising the steps of:
when the vertical axis of the level is positioned so as to be inclined in
space, determining the correction of the sighting axis, with respect to
amount and direction, by the computer from the angle .alpha. of the
inclination component of the vertical axis in the sighting direction,
which angle .alpha. is measured in the measuring direction of the biaxial
clinometer, and
determining the image erection correction of a cross-line or crosshair
displayed on the screen or a monitor by the computer from an angle .beta.
of the inclination component of the vertical axis transverse axis
transverse to the sighting direction, which angle .beta. is measured in
the other measuring direction of the clinometer.
7. The process according to claim 6, wherein a correction value of the
level comprising two height correction values is recorded, wherein a first
height correction value .DELTA.h.sub.1 =f.times.sin
.alpha..apprxeq.f.times.arc .alpha. is determined by which the center
pixel on the CCD receiver matrix and screen is to be displaced in order to
mark the horizontal line of sight at the image of the graduated staff on
the screen, and a second height correction value .DELTA.h.sub.2
=s.times.sin .alpha..apprxeq.s'arc .alpha. is determined which compensates
for the distance of the object-side principal point of the objective to
the sighting axis diverging from the horizontal, where f represents the
focal length of the objective, s represents the distance of the
object-side principal point of the objective from the intersection of the
vertical axis and sighting axis, and .alpha. represents the angle of
inclination of the sighting axis of the objective in relation to the
horizontal in the sighting direction and the angle of inclination of the
vertical axis relative to the normal axis in the sighting direction, and
in that the reading of the graduated staff is corrected by the computer
based on these two height correction values .DELTA.h.sub.1 and
.DELTA.h.sub.2.
8. The process according to claim 6, wherein, for purposes of height
correction on the screen, the graduated staff image or the image crosshair
of the screen is displaced vertically for height correction on the screen,
and wherein the image of the graduated staff on the screen or the image
crosshair of the screen is rotated until a vertical position of the
graduated staff image or of the image crosshair is achieved.
Description
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to an electronic level with a clinometer and a
process for video sighting or targeting of a graduated staff of at least
one target at a distance, from the level in accordance with the preamble
of the first patent claim, wherein the level, as a dumpy level or quickset
level, has a high degree of automation at low manufacturing cost.
b) Description of the Related Art
DD 291 141 discloses an arrangement for leveling the line of sight of
levels, wherein the arrangement comprises a telescope with a sighting
axis, including an objective with sliding lens, a graticule and an
eyepiece. The arrangement further contains a photoreceiver device with a
differential photoelement and a piezo-actuator by means of which the
graticule can be adjusted in such a way, depending on the signals which
are supplied by a clinometer and appropriately processed by a
microprocessor, that a leveling of the telescope axis is achieved.
JP 60-25 413 describes a level with a digital graduated staff at the
target. In this case, a light beam is sent to the graduated staff via a
beam splitter from a light source arranged in the level and an image of
the graduated staff is received by an optical television camera system and
displayed on a screen. The determined data are stored in a computer and
evaluated in a suitable manner. The screen itself is a liquid crystal
display with elements arranged in a matrix. The objective can be focused
manually by a sliding lens.
Further, JP 5-272 970 discloses an automatic level which comprises a matrix
receiver with a screen, wherein image signals from a CCD-camera are
converted into corresponding digital signals by an analog-to-digital
converter and are stored in a data storage. The CCD-camera has a focusable
objective with a sliding lens.
In the above-mentioned arrangements, focusable objectives are always
provided for sharp imaging of the staff graduation on a photoreceiver
arrangement or CCD arrangement.
In order to do without focusing, a device for leveling purposes (DE 195 04
039 C1) was provided with imaging optics and a spatially-resolving
optoelectronic detector for image recording. In this case, the imaging
optics are divided into pupil zones imaging in different ways for
different depth of focus ranges; different partial areas of the detector
are allocated to the pupil zones. While this device does avoid focusing,
the different imaging optics are relatively uneconomical.
In a process for geometric height measurement according to DE 39 16 385, in
a manner analogous to the signals of a clinometer arranged in a
measurement device independent from a telescope, the reference point for
the horizontal position of the measurement device is provided on the
center pixel of a CCD array and, when the device is tilted, is displaced
in such a way that its position corresponding to the respective
inclination of the device determines the intersection point of the
horizontal sighting axis for a pixel or for the area between two pixels.
OBJECT AND SUMMARY OF THE INVENTION
It is the primary object of the invention to provide an electronic level
and a process for video sighting of a graduated staff which ensures a high
degree of automation of measurements at low manufacturing costs and while
economizing on optical and mechanical structural component parts and in
which large inclinations of the vertical axis can be compensated.
This object is met, according to the invention, in an electronic level
which comprises a clinometer, an image receiving device having a telescope
with an objective and with a CCD receiver matrix and with a screen for
displaying the image of a graduated staff which is set up at a target and
provided with a coded graduation, a vertical axis which is rotatable about
the level, a leveling device for alignment and rough leveling of the level
with respect to the graduated staff, an input unit for entering
measurement data and a power supply unit and a computer for processing the
measurement data, calculating measurement values and for image evaluation.
The image receiving device comprises a CCD receiver matrix which is
operated in video clock. The objective or the CCD receiver matrix is
arranged in a fixed position relative to the vertical axis. The objective
and CCD receiver matrix is adjustable relative to one another. The
clinometer is assigned in a fixed manner for measuring the deviation of
the position of a sighting axis relative to the horizon. The sighting axis
is formed by a center pixel of the CCD receiver matrix.
The invention also encompasses a process for using the electronic level.
The level according to the invention is a camera level, as it is called,
which basically includes only the objective, the clinometer, the vertical
axis and an endless slow-motion tangent screw for sighting the graduated
staff, a leveling device (tribrach or ball joint) and an image detection
and image display system. The image detection system includes a CCD
receiver matrix with the center pixel which, together with the object-side
principle point of the objective, serves to determine the line of sight
which is assigned in a fixed manner to the clinometer which measures, in a
known manner, the deviation of the position from the horizontal. The CCD
receiver matrix itself is operated in pixel clock or video clock and
accordingly supplies moving images of the distant target to be measured.
In order that the position of a vertical axis inclined in space can also be
taken into account in measurements with the level, the data supplied by
the clinometer are included in the processing by the computer. Therefore,
it is possible that the level need no longer be exactly leveled. In a case
such as this, the graduated staff image would appear inclined on the
screen. For this reason, the level is provided not only with image
evaluating electronics and corresponding software, but also with a
computer which calculates an appropriate height correction by means of the
data supplied by the clinometer and applies this to the reading of the
graduated staff. In this way, with the aid of the data from the clinometer
which supplies data in two axes, a crosshair on the screen can be adjusted
so as to be vertical and moved in the horizon in order to simultaneously
carry out an alignment of the line of sight in the same way as with a
well-leveled level. Accordingly, it is possible to work with a skewed
level in the same way as with a well-leveled level.
In order to obtain correction values in a particularly simple manner and to
use these correction values for measurement correction in a corresponding
manner, the forward, i.e., object-side, principal point of the objective
advantageously lies in the intersection of the sighting axis and vertical
axis or at a fixed distance from this intersection.
Further, it is advantageous when the CCD receiver matrix and the objective
are displaceable relative to one another by adjusting means in the
direction of the optical axis of the objective for focusing the graduated
staff image, wherein the CCD receiver matrix or the objective is arranged
in a fixed position relative to the vertical axis, and when the
displacement path and the displacement direction of the matrix and/or of
the objective can be determined from the image data supplied by the
receiver elements of the matrix by means of an image evaluating system,
known per se.
Further, the display unit is advantageously provided with a screen having a
diaphragm for blocking out ambient light and an arrangement is provided
which controls the contrast of the screen as a function of the ambient
light and which is connected with the computer. In this way, the screen
can be properly viewed even under unfavorable light conditions.
A process for video sighting with the level constructed according to the
invention, wherein a graduated staff set up at a distant target point is
sighted, is characterized in that when the vertical axis of the level is
positioned so as to be inclined in space the correction of the sighting
axis, with respect to amount and direction, can be determined by the
computer from the angle a of the inclination component of the vertical
axis in the sighting direction, which angle a is measured in the measuring
direction of the biaxial clinometer, and the image erection correction of
a cross-line displayed on the screen can be determined by the computer
from an angle .beta. of the inclination component of the vertical axis
transverse to the sighting direction, which angle .beta. is measured in
the other measuring direction of the clinometer.
In order to carry out a corresponding correction of the measurement values,
it is advantageous when a correction value of the level comprising two
height correction values is recorded, wherein there is determined a first
height correction value .DELTA.h.sub.1 =f.times.sin
.alpha..apprxeq.f.times.arc .alpha. by which the center pixel on the CCD
receiver matrix and screen is to be displaced in order to mark the
horizontal line of sight at the image of the graduated staff on the
screen, and wherein there is determined a second height correction value
.DELTA.h.sub.2 =s.times.sin .alpha..apprxeq.s.times.arc .alpha. which
compensates for the distance of the object-side principal point of the
objective to the sighting axis diverging from the horizontal, where f
represents the focal length of the objective, s represents the distance of
the object-side principal point of the objective from the intersection of
the vertical axis and sighting axis, and .alpha. represents the angle of
inclination of the sighting axis of the objective in relation to the
horizontal in the sighting direction and the angle of inclination of the
vertical axis relative to the normal axis in the sighting direction, and
when the reading of the graduated staff is corrected by the computer based
on these two height correction values .DELTA.h.sub.1 and .DELTA.h.sub.2.
In order to be able to work in the same way as with a well-leveled level,
the graduated staff image or the image crosshair of the screen are
displaced vertically for height correction on the screen. For the purpose
of image (target) erection correction, the image of the graduated staff on
the screen or the image crosshair of the screen is rotated until a
vertical or normal position of the graduated staff image or of the image
crosshair is achieved.
The invention will be described more fully hereinafter in an embodiment
example.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 shows the construction of the level in a simplified view;
FIG. 2 shows a simplified ray diagram; and
FIG. 3 shows a view of the screen.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The electronic level shown in FIG. 1 comprises a stationary tribrach 1 on
which a top part 2 is mounted so as to be rotatable about a vertical axis
STA. The tribrach 1 itself can be a leveling device, known per se, with
foot screws 3 or with a ball head or wedge disks by which the level can be
leveled. The vertical axis STA is shown in the Figures as a dash-dot line.
The top part 2 carries all of the elements or component assemblies needed
for the operation of the level. Located in the top part 2 are an objective
4 whose optical axis coincides with the sighting axis ZA, a CCD receiver
matrix 5 formed of CCD receivers as image receiving device, and a screen 6
with diaphragm 7 for blocking out interfering extraneous light. The
combination of objective 4 and CCD receiver matrix 5 represents, in
principle, a video camera, wherein the CCD receiver matrix 5 is preferably
operated in video clock and accordingly supplies moving images. The
objective 4 is arranged in a fixed position relative to the vertical axis
STA such that its object-side principal point H coincides with the
intersection A of the vertical axis STA and sighting axis ZA. The
principal point H can also be arranged at a fixed distance s from this
intersection point A as is illustrated, for example, in FIGS. 1 and 2. The
distance s is taken into account as a device constant in determining the
measurement values, e.g., in the height corrections, as will be further
described hereinafter. Further, there are provided in or on the top part 2
a power supply unit 8, an input unit 9, e.g., a keyboard for entering
data, a preferably multiaxial clinometer 10, a computer 11 and a
corresponding electronics subassembly 12 for image evaluation and for
controlling the individual functions, as well as subassemblies and a
monitor 13 for focusing the objective 4 on the CCD receiver matrix 5 in
order to obtain a sharp image of a graduated staff (not shown) set up at a
distance from the level. This monitor 13 can also be provided at the rear
of the level. An endless drive control 14 is advantageously provided for
fine adjustment of the objective 4 of the level telescope on the graduated
staff representing the target. A rough leveling of the device can be
carried out by displacing the foot screws 3 in accordance with a bubble
level 15 which can be arranged in the upper part of the level.
A biaxial clinometer 10 is provided for measuring inclination and for
determining and taking into account the inclined position of the level,
wherein inclinations in the direction of the sighting axis ZA and in a
direction orthogonal thereto in the horizontal plane are determined and
included in further measurements by means of this clinometer 10. However,
the two measurement directions of the clinometer 10 can also enclose an
angle with one another other than a right angle.
In order to focus the objective 4 on the plane of the CCD receiver matrix
5, these two subassemblies are adjustable relative to one another. For
this purpose, as is shown in FIG. 1, a tube 16 carrying the CCD receiver
matrix 5 is mounted in a guide 17 and is displaceable in the direction of
the sighting axis by a drive 18. Focusing can be carried out automatically
by means of an integrated image evaluating system. The latter calculates
data from the image of the graduated staff and causes the focusing to be
carried out by means of a corresponding signal by adjusting the distance
between the objective 4 and the CCD receiver matrix 5 by a drive 18. When
the image evaluating system has detected a sharp image, the focusing
process is stopped; the graduation of the graduated staff set up at the
target can now be read.
The conditions to be met for correction functioning of the level can be
seen from the simplified ray diagram of the level shown in FIG. 2. The
vertical axis STA and therefore also the objective 4 of the level
telescope are shown inclined by angle a to the staff horizon. The ray
characterizing the horizon traverses the object-side focal point F of the
objective 4 and impinges on the object-side principal plane H of the
objective 4. This focal point ray, as it is called, is imaged by the
objective 4 parallel to the sighting axis ZA in the image point L.sub.1
situated in the plane M.sub.1 of the CCD receiver matrix 5. In case of
infinite target distance, the focal plane M.sub.1 forms the plane in which
the image-side focal point F' of the objective 4 is situated. As the
graduated staff approaches the level, the distance of the focal plane from
the objective 4 increases. The location of the focal plane M.sub.2 with
focal point L.sub.2 for the shortest possible target distance (about 3 m)
is shown by way of example in FIG. 2. The CCD receiver matrix 5 is moved
and adjusted relative to the objective 4, or vice versa, in a
corresponding manner in the interval between M.sub.1 and M.sub.2 by means
of the focusing system.
At the same time, angle a is determined by the clinometer and a first
correction value .DELTA.h.sub.1 according to the equation .DELTA.h.sub.1
=f.times.sin .alpha..apprxeq.f.times.arc .alpha. is calculated by the
computer 11 and the center pixel MP which is located in F' at infinite
target distance is displaced by L.sub.1, where f represents the focal
length of the objective 4. When focusing on different distances to the
graduated staff, the distance of focal points L.sub.1 and L.sub.2 from the
sighting axis ZA remains the same.
The reference point for height measurement with the level is the
intersection A which lies on the vertical axis STA and sighting axis ZA.
Therefore, an additional, second correction value .DELTA.h.sub.2
=s.times.sin .alpha..apprxeq.s.times.arc .alpha. which takes into account
the distance of the intersection A from the horizon must be determined in
reading the graduated staff, so that the total height correction is
.DELTA.h=.DELTA.h.sub.1 +.DELTA.h.sub.2. The correction value
.DELTA.h.sub.1 depends only on the angle of inclination a and on the focal
length f of the objective 4 and is determined by the clinometer 10 with
respect to amount as well as direction. Accordingly, a positive or a
negative sign indicates whether the center pixel MP is to be displaced
upward or downward. The focal length f is a fixed device constant which is
taken into account as constant value by the computer in the corresponding
calculations.
The distance s of the principal point H of the objective 4 from the
intersection A is also a device constant which can be entered in a fixed
manner and is then automatically taken into account.
However, the situation is different when the objective 10 is displaced for
focusing and the CCD receiver matrix is positioned at a fixed distance
from the vertical axis STA. In this case, the video camera must not only
carry out an autofocusing, but the distance to the graduated staff must
also be measured in order to determine the instantaneous focal length for
the change of s (distance of objective 10 from the vertical axis STA).
The height correction value .DELTA.h.sub.2 is generally small when the
level is well-leveled beforehand and the objective 4 is not arranged too
far from the vertical axis STA. The value .DELTA.h.sub.2 is zero when the
principal point H of the objective 4 coincides with intersection A.
The position of the center pixel MP in the case of a well-leveled level is
shown on the screen of the monitor 13 in FIG. 3. If the level is tilted,
the image 19 of the graduated staff on the screen occupies the position
shown in dashes which is rotated by a transverse angle of inclination
.beta. with respect to the horizontal position of the crosshair 20. This
angle .beta. is likewise determined by the clinometer 10. The inclined
image 19 is then rotated by angle .beta. into the horizontal position in
the computer 11 by means of an image erection correction, so that it
conforms to the crosshair 20.
While the foregoing description and drawings represent the preferred
embodiments of the present invention, it will be obvious to those skilled
in the art that various changes and modifications may be made therein
without departing from the true spirit and scope of the present invention.
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